Republican Rep. Rick Berg, running for Senate in North Dakota, has close ties to a controversial property management company that has been the target of dozens of tenant complaints, been cited for alleged fire safety violations and received a less than stellar grade from the Better Business Bureau.

Berg, one of the wealthiest members of Congress, personally owns apartment buildings run by Goldmark Property Management Inc., one of North Dakota’s largest landlords. Employees of the firm and related companies, including business associates Berg has known for decades, have donated tens of thousands of dollars to Berg and GOP committees to back his runs for federal office.

Yet Berg does not, as alleged by Democrat Heidi Heitkamp, have any formal legal ties to or control over Goldmark Property Management. And even some Democrats have winced at her attempts to link the company’s actions to proposals to change Social Security and other entitlement programs.

Berg’s finances have become a hot issue in a surprisingly tight race that could determine control of the Senate. With the battle for the Senate majority down to a handful of races, the two candidates and outside groups have poured millions of dollars into TV ads in a state that hasn’t seen a competitive Senate race in more than 25 years.

Berg’s business dealings have drawn harsh criticism from Democrats, who are trying to turn one of his strongest selling points into a political liability. These Democratic attacks have drawn a vigorous defense from the Berg campaign and national Republicans, who had hoped North Dakota would be a slam-dunk as a GOP Senate seat pickup.

The picture of Berg’s finances — put together by POLITICO through public documents from North Dakota — reveal a complex combination of ownership structures. Berg’s ties to the executives who run the Goldmark-related companies are extensive.

For example, Goldmark Schlossman Commercial Real Estate Services — a related firm that Berg helped found in the mid-1990s — is located at the same address in Fargo and shares the same phone number as Goldmark Property Management, and leases space from it as well.

And during a 26-year career in the North Dakota Legislature, including holding several GOP leadership posts, Berg backed legislation that would buttress landlords’ legal and financial positions, according to legislative records from that period.

Berg has angrily countered questions about his business dealings by accusing Heitkamp, a former state attorney general, of hitting “a new low in North Dakota politics” by falsely claiming he “owns” Goldmark Property Management, a company “in which he holds no employment, management, ownership, shareholding, or invested interest — nor has he ever.”

However, the true picture of Berg’s ties to the firm is more complex than both candidates have let on.

Berg’s version of events — a college whiz kid turned successful businessman and state legislator — is a key facet of his success story.

Berg first began working with three associates — Dale Lian, James Wieland and Kenneth Regan, all Goldmark Property Management officers — in 1982, when the quartet created Midwest Management Corp., state records show.

“In his senior year of college, Rick partnered with a few friends to start a small real estate business in Fargo,” Berg says in his official biography. “With nothing more than a loan, a vision, and a lot of hard work, what began as a business idea among friends grew into what is now Goldmark Schlossman Commercial Real Estate Services."

Berg’s personal wealth is now estimated at more than $21 million, according to his annual financial disclosure reports, making him one the richest members of Congress. Since these reports only include a broad range of values, his actual net worth could be significantly above that level.

Berg ended his relationship with MMC in 1987, according to his campaign. MMC then changed its name to Goldmark Property Management in 1994.

In 1996, Berg founded — again with Lian, Wieland and Regan — Goldmark Commercial Corp. The firm was involved in commercial real-estate sales and leasing. In 2005, the company revised its name to Goldmark Schlossman Commercial Real Estate Services Inc.

A 1995 real-estate license issued to Berg identifies him as an employee of Goldmark Property Management.

Berg insists there is no “legal affiliation” between the two firms Goldmark Schlossman Commercial Real Estate Services and Goldmark Property Management, despite the fact that they share many of the same corporate officers and operate out of the same location.

However, Goldmark Property Management’s website listed Berg as a senior vice president of the company until last month, when the Web page was scrubbed. Berg has acted as a public spokesman for Goldmark Property Management in the past, and the firm was listed as his employer in a campaign donation made in 2000. Berg now says this was a clerical error.

Goldmark-related employees and relatives have donated $27,900 directly to Berg’s Senate campaign this cycle, campaign records show. Another $20,000 went to the National Republican Senatorial Committee via the Berg Victory Committee, a joint fundraising entity created by the NRSC and Berg campaign.

Wieland, Berg’s former business partner, gave $5,000 to the North Dakota Republican’s leadership PAC.

Berg has nearly doubled Heitkamp’s fundraising for the cycle. Berg has taken in $4 million while Heitkamp has raised $2.1 million, Federal Election Commission records show.

In 2010, as Berg ran successfully for a House seat, Goldmark-related employees donated nearly $29,000 to his campaign, as well as another $30,000 to the North Dakota Republican Party.

In 1984, just as his real-estate career was getting started, the then-25-year-old Berg was elected to the state Legislature. Berg served in that body until 2010, when he was elected to Congress.

During Berg’s tenure in the state Legislature, he sponsored or backed legislation that would have given landlords increased authority to evict unruly tenants; required tenants to pay immediate restitution to landlords for losing challenges to eviction notices; called for bigger security deposits by new tenants; opposed rent control and mandatory fire sprinklers; and voted for tax relief for property owners, including landlords.

Berg also opposed a bill to set up an independent organization to settle tenant-landlord disputes.

Despite the numerous connections to Goldmark Property Management and his former business partners, Berg insists Heitkamp erred by linking him directly to the firm.

“I’ve had absolutely no involvement in the company she cited in her ad; no ownership, no management, no employment, no involvement,” Berg said at a press conference in North Dakota on Sept. 13. Berg actually left Capitol Hill despite votes later that day in order to hold the event, showing the importance of the controversy to his campaign.

Heitkamp has tried to counter Berg’s business record by highlighting the controversies surrounding Goldmark Property Management, which controls more than 9,000 units with over 25,000 residents, a sizable chunk of North Dakota’s 670,000-plus residents.

Heitkamp attempted to link Goldmark Property Management — and Berg’s alleged involvement with it — to efforts to privatize Social Security, which even Democratic operatives will privately admit is a stretch.

“Maybe it shouldn’t be a surprise that Rick Berg would use his business experience to privatize Social Security,” Heitkamp asserted in one of her ads bashing the freshman GOP lawmaker. “He’s voted time and again to risk Social Security funds in the stock market. Rick Berg, treating seniors the same way he treats his tenants.”